Schwartz first described elevated IOP in association with a rhegmatogenous retinal detachment, and Matsuo later demonstrated photoreceptor outer segments in the aqueous humor in a group of similar patients. The postulated mechanism of IOP elevation is that a chronic rhegmatogenous retinal detachment leads to the liberation of photoreceptor outer segments, which, migrating through the retinal tear, reach the anterior chamber and impede aqueous outflow through the trabecular meshwork.